This is the second submission of an HSR&D CDA-2 proposal to provide four years of salary support to Hillary Mull, Ph.D. toward her goal of developing an independent VA health services research career. Dr. Mull is an Investigator at the Center for Healthcare Organization and Implementation Research (CHOIR), a joint HSR&D Center of Innovation (COIN) of two former Centers of Excellence, the Center for Organization, Leadership, and Management Research (COLMR) at the VA Boston Healthcare System and the Center for Healthcare Quality Outcomes, and Economics Research (CHQOER) at the Bedford VAMC. Dr. Mull is also a Research Assistant Professor at the Boston University School of Medicine (BUSM) in the Department of Surgery. This CDA proposal outlines research and training plans that will set the foundation for Dr. Mull's future as an independent investigator with significant experience in applying healthcare informatics tools to detect outpatient adverse events (AEs). Her CDA goal is to improve quality and safety in outpatient surgery through the development and implementation of an AE surveillance system that uses trigger tools (TTs) to screen outpatient surgical data in the VA Corporate Data Warehouse (CDW). TTs are an emerging method that can increase the efficiency of the chart review process. TTs screen electronic clinical data to flag cases with a high probability of having an AE; cases are then briefly reviewed by a nurse to confirm the presence of any AE, and to rate the severity of the harm. In Aim 1, Dr. Mull will create a database of outpatient surgeries in VA through a mixed methods approach that uses qualitative interviews with surgical stakeholders to identify relevant variables associated with select TT outcomes (e.g., visit to the emergency department following outpatient surgery). These variables will be drawn from a modified Donabedian conceptual framework of structural, procedural and patient characteristics. Outpatient surgeries and surgical characteristics will be identified in VA electronic data sources including the CDW. In Aim 2, Dr. Mull will develop a TT surveillance system for outpatient surgery that uses predictive modeling to detect AEs among trigger-flagged cases. Aim 3 will implement the TT system in two VA surgical programs. Dr. Mull will use methods outlined in the Consolidated Framework for Implementation Research (CFIR) to conduct a formative evaluation of the implementation process, and summative evaluation of the effect of the TT system on AE rates and outpatient surgical quality. Dr. Mull's training plan focuses on bolstering her knowledge of healthcare informatics, qualitative program evaluation, and implementation science. Dr. Mull has a team of expert mentors (including Drs. Amy Rosen, Marty Charns, Kamal Itani, and Mary Hawn) and consultants (Drs. Peter Rivard, Steven Pizer, and Kathleen Hickson) who are qualified and strongly committed to helping her complete her CDA goals and establish herself as an independent HSR&D investigator. This mentorship, along with the rich resources available at CHOIR, will ensure that Dr. Mull has all the support necessary to meet her research and training aims. She will have access to CHOIR facilities, resources, and collaborations with exceptional HSR&D-funded investigators. Through this CDA, and in a QUERI SDP proposal planned for year 2 and an HSR&D pilot planned for year 4 of the CDA work, Dr. Mull proposes to develop and implement an AE surveillance system designed for outpatient surgery that can be used to target quality improvement efforts. The system can be broadly applicable to other outpatient settings, something we will explore in future research. Detecting and monitoring AEs in outpatient settings using existing data in the VA CDW is consistent with HSR&D funding priority C- Healthcare Informatics. This field of research will become even more important as care increasingly transitions from the hospital to the outpatient setting. Our results will provide much needed information about VA outpatient surgery to the research and surgical communities as they continue to measure and improve the quality of surgical care to our Veterans.